Method of and means for regulating the speed of electric motors.



Patented Dec. 7, 1909 Inventor, Robert/1. FqgQns;

R. H. ROGERS.

APPLICATION rILnn we. 5. 1908.

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METHOD OF AND MEANS-FOB. BEGULATING THE SPEED OF ELECTRIC MOTORS.

UNITED STATES PATENT OFFICE.

ROBERT H. ROGERS, 0F SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRICCOMPANY, A CORPORATION OF NEW YORK.

METHOD OF AND MEANS FOR REGULATING THE SPEED OF ELECTRIC MOTORS.

Specification of Letters I'atent.

Patented Dec. '7, 1909.

7 Application filed August 5, 1908. Serial No. 447,065.

To all whom it may concern:

Be'it known that I, ROBERT E. ROGERS, a citizen of the United States,residing at Schenectady, in the county of Schenectady and State of NewYork, have invented certain new and useful Improvements in Meth- 'ods ofand Means for Regulating the Speed when lightly loaded. Heretofore, whensuch motors have been used under conditions in'which their load islikely to be suddenly thrown off or greatly reduced, means such asunderload relays, have been --provided to open the motor circuit. If themotor is the trolley motor on a, crane, the load is often reduced to avery small amount by the swin ing of the load in the direction of itstrave and upon the opening of the motor circuit, the oraneman mustdescend from tle crane in order to again closeit. This is veryinconvenient and causes great loss of time. To avoid this difliculty, Iprovide the motor with two field windings, and regulate its' speedbyoperating the motor as a series 'Inotor whenheavily loaded and as acumulative compound motor when lightly loaded i i In another aspect, myinvention consists in the combination with an electric motor having twofield windings .wound cumulatively, of means for maintaining the circuitof one of said windin s open when the motor isheavily loaded an forclosing said circuit when themotor is lightlyloaded.

In a still narrower aspect my invention consistsin the combination of aseries motor having a cumulative shunt field winding, of means actuatedby the current supplied to the armature pf said motor for maintainingthe circuit of the shunt field winding open when a large amount ofcurrent is-supplied and for closing said circuit when a small amount ofcurrent is supplied.

For a better understanding of my invention, reference may be had to thefollowing description taken in connection with the accompanying drawingwhich shows diagramrelates to electric motors,

matically the arrangement of the connections of t motor according to myinvention.

Referring to the diagram, in order to prevent the motor A from racingwhen operating under a light load,.I provide two field windings B and Cwound cumulatively, one of which remains open at the contacts D when themotor is heavily loaded but when the motor is lightly loaded the circuitof this field winding C is closed. The field winding B is supplied withcurrent from the lines L in series with the armature of the motor. Thefield winding G is a shunt winding, which may be connected across thelines L. As pointed out above, the circuit of this winding may be madeand broken at the contacts D of the relay E. The actuating coil F ofthis relay is also in series with the armature of the motor. This relayis arranged to lift up its armature and keep the circuit across thecontacts D open when a heavy current flows through its actuating coiland to close the circuit across its contacts when very little currentflows through its actuating coil, either by the action of gravity asshown, or by any other suitable means. The relay is provided with adash-. pot Q to retard its action upon the opening of its contacts so asto break the circuit of the shunt field winding C slowly. It willtherefore be seen-that when the machine A is carrying a load, acomparatively large current flows through the lines L, the series fieldB, the motor armature and the actuating coil F of the relay. The large.current flowing through the coil F maintains the circuit across thecontacts D open so that no current is supplied to the field winding C,and the motor A operates as a series motor. In-case, however, the loadis taken off the motor because of the swinging of the bucket or for anyother cause the current taken by the motor is greatly reduced and ittends to race because of the weakened field. The reduction of thecurrent supplied to the motor, however, lessens the amount flowingthrough the coil F, it releases its armature and t e circuit is closedacross the contacts D, thereby supplying excitation to the field windingC. This winding being wound cumulatively, that is, wound so that itproduces a magnetic field in the same direction as the series fieldwinding B, adds to the. field of the motor and slows it down, the

' States, is,

be used in connection with motors driving hoists or other apparatus, orwith dynamo electric machines generally as, for example,

. with machines which ordinarily run as generators, but under certainconditions may operate as motors, and I aim in the appended claimsto-cover all such applications of my invention.

What I claim as new and desire to secure by Letters Patent of theUnited 1. The method of regulating the speed of an electric motor havingtwo field windin s wound cumulatively, which consists in maintaining oneof said field circuits open when the motor is heavily loaded and closingsaid field circuit when said motor is lightly loaded.

2. The method, of regulating the speed-of a series motor having acumulative shunt field winding, which consists in maintaining said shuntfield winding open when the motor is heavily loaded and closing saidshunt field circuit when said motor is lightly loaded.

3. The method of regulating the speed of an electric motor having ashunt and series field winding, which consists in operating said motoras a series motor when under load and as a cumulative compound motorwhen lightly loaded.

4. In combination-with an electric motor having two field windings woundcumulatively, means for maintaining the circuit of one of said windingsopen when the motor is heavily loaded and for closing said circuit whenthe motor is lightly loaded.

5. In combination with an electric motor having two field windings woundcumulatively, means actuated by the current sup- I plied the armature ofsaid motor for maintaining the circuit of one of said windings open whena large amount of current is supplied and for closing said circuit when.a

small amount of current is supplied.

6. In combination with an electric motor 8. In combination with a seriesmotor.

having a cumulative shunt field winding, means actuated by the currentsupplied the armature of said motor for maintaining the shunt fieldwinding circuit open when a large amount of current is supplied and forclosing said circuit when a small amount of current is supplied. 4

9. In comb nation with a series motor having a cumulative shunt fieldwinding,-

a relay actuated by the current supplied the armature of said motor formaintaining the shunt field winding circuit open when a large amount ofcurrent is supplied and for closing said circuit when a small amount ofcurrent is supplied.

10. In combination with a series motor having a cumulative shunt fieldwinding, a relay for maintaining the circuit of said shult field windinopen when the motor is' heavily loaded an for closin said circuit whenthe motor is lightly loaded.

In witness whereof, I have hereunto set my hand this 4th day of Au ust,1908.

- ROBERT ROGERS. l/Vitnesses BENJAMIN B. HULL, HELEN 'ORFORD.

